Cellulose solutions in ionic liquids

ABSTRACT

The present invention relates to a solution comprising cellulose and an ionic liquid comprising anions and cations as solvent, wherein the cations comprise at least one atom selected from the group consisting of nitrogen, oxygen, sulfur and phosphorus which is present in protonated form, its preparation and use for physical and chemical treatment.

The present invention relates to a solution comprising cellulose and anionic liquid as solvent, a process for preparing it and its use.

Cellulose is a very versatile raw material. In the textile industry,cellulose is, for example, the most important constituent of fiber rawmaterials, in particular of cotton.

Cellulose can be used unchanged or after physical or chemical treatment.In the latter two cases, it is advantageous for cellulose to be inpreferably completely dissolved form in a solvent. However, cellulose isinsoluble in most solvents.

Cellulose is soluble as a copper chelate complex in some coppersolutions. Regenerated cellulose can be obtained by precipitation of thecellulose. However, such copper solutions are not very suitable assolvents for cellulose in the case of physical or chemical treatment ofthe cellulose.

For this reason, the systems known, inter alia, as ionic liquids in theliterature were proposed very early on as solvents for cellulose.

Thus, U.S. Pat. No. 1,943,176 describes the dissolution of cellulose inbenzylpyridinium chloride.

As an example of an ionic liquid, benzylpyridinium chloride is a saltwhich is present in molten form and thus as a liquid at comparativelylow temperatures.

Ionic liquids are becoming increasingly important as solvents, e.g. forcarrying out chemical reactions. Peter Wasserscheidt, Angew. Chem. 2000,112, 3926-3945, for example, gives an overview of the use of ionicliquids in transition metal catalysis.

Ionic liquids which are present in the liquid state even at roomtemperature are described, for example, by K. N. Marsh et al., FluidPhase Equilibria 219 (2004), 93-98, and J. G. Huddleston et al., GreenChemistry 2001, 3, 156-164.

DE-A 102 02 838 describes the use of ionic liquids for separating acidsfrom chemical mixtures.

Owing to the good solvent capabilities of ionic liquids, their use forthe dissolution of cellulose is also proposed in the more recentinternational patent application WO-A 03/029329. However, it isemphasized there that the ionic liquids should comprise cations whichcomprise a quaternary ammonium ion which should be quaternized by alkylgroups, in particular methyl.

Although the characteristics of the cellulose-comprising solution andits preparation described in WO-A 03/029329 have good results, there isa need to provide improved solutions.

It is therefore an object of the present invention to provide a solutionof dissolved cellulose which displays improved properties.

The object is achieved by a solution comprising cellulose and an ionicliquid comprising anions and cations as solvent, wherein the cationscomprise at least one atom selected from the group consisting ofnitrogen, oxygen, sulfur and phosphorus which is present in protonatedform.

It has been found that the preparation of cations by means of hydrogen(protonation), in particular by quaternization of the nitrogen, canresult in improved properties. In particular, it has been found thatsolutions comprising ionic liquids are easier to work up. Thus, theionic liquids can be converted by addition of a base into a distillableform, which makes them easier to separate off.

The protonation can be effected at one or more identical or differentheteroatoms (N, O, S, P). Apart from generation of a positive charge byprotonation, further positive charges can also be present in thecations, for example as a result of alkylation of a nitrogen.

However, the cations preferably have at least one nitrogen atom which ispresent in protonated form as ammonium cation.

The cellulose to be dissolved can originate from, for example,regenerated cellulose, fibrous cellulose, wood fibers, lint, cotton orpaper.

It is preferred that, in the solution of the present invention, morethan 1% by weight of cellulose, based on the total weight of thesolution, are completely dissolved. More preferably, more than 3% byweight, particularly preferably more than 5% by weight and in particularat least 7% by weight, based on the total weight of the solution, arecompletely dissolved.

Advantageously, up to 35% by weight of cellulose, based on the totalweight of the solution, can be completely dissolved. Furthermore, up to25% by weight of cellulose, based on the total weight of the solution,can be completely dissolved. Solutions in which up to 15% by weight ofcellulose are completely dissolved are especially suitable forparticular applications.

For the purposes of the present invention, ionic liquids are preferablysalts of the general formula

(A) salts of the general formula (I)[A]_(n) ⁺[Y]^(n−)  (I),where n is 1, 2, 3 or 4, [A]⁺ is a quaternary ammonium cation, anoxonium cation, a sulfonium cation or a phosphonium cation and [Y]^(n−)is a monovalent, divalent, trivalent or tetravalent anion;

(B) mixed salts of the general formulae (II)[A¹]⁺[A²]⁺[Y]^(n−)  (IIa), where n=2;[A¹]⁺[A²]⁺[A³]⁺[Y]^(n−)  (IIb), where n=3;[A¹]⁺[A²]⁺[A³]⁺[A⁴]⁺[Y]^(n−)  (IIc), where n=4, andwhere [A¹]⁺, [A²]⁺, [A³]⁺ and [A⁴]⁺ are selected independently fromamong the groups mentioned for [A]⁺, and [Y]^(n−) is as defined under(A); or

(C) mixed salts of the general formulae (III)[A¹]⁺[A²]⁺[A³]⁺[M¹]⁺[Y]^(n−)  (IIIa), where n=4;[A¹]⁺[A²]⁺[M¹]⁺[M²]⁺[Y]^(n−)  (IIIb), where n=4;[A¹]⁺[M¹]⁺[M²]⁺[M³]⁺[Y]^(n−)  (IIIc), where n=4;[A¹]⁺[A²]⁺[M¹]⁺[Y]^(n−)  (IIId), where n=3;[A¹]⁺[M¹]⁺[M²]⁺[Y]^(n−)  (IIIe), where n=3;[A¹]⁺[M¹]⁺[Y]^(n−)  (IIIf), where n=2;[A¹]⁺[A²]⁺[M⁴]²⁺[Y]^(n−)  (IIIg), where n=4;[A¹]⁺[M¹]⁺[M⁴]²⁺[Y]^(n−)  (IIIh), where n=4;[A¹]⁺[M⁵]³⁺[Y]^(n−)  (IIIi), where n=4; or[A¹]⁺[M⁴]²⁺[Y]^(n−)  (IIIj), where n=3, andwhere [A¹]⁺, [A²]⁺ and [A³]⁺ are selected independently from among thegroups mentioned for [A]⁺, [Y]^(n−) is as defined under (A) and [M¹]⁺,[M²]⁺, [M³]⁺ are monovalent metal cations, [M⁴]²⁺ is a divalent metalcation and [M⁵]³⁺ is a trivalent metal cation.

The ionic liquids preferably have a melting point of less than 180° C.The melting point is more preferably in the range from −50° C. to 150°C., still more preferably in the range from −20° C. to 120° C. and mostpreferably below 100° C.

Compounds which are suitable for forming the cations [A]⁺ of ionicliquids are, for example, known from DE 102 02 838 A1. Thus, suchcompounds can comprise oxygen, phosphorus, sulfur or in particularnitrogen atoms, for example at least one nitrogen atom, preferably 1-10nitrogen atoms, particularly preferably 1-5 nitrogen atoms, veryparticularly preferably 1-3 nitrogen atoms and in particular 1-2nitrogen atoms. If appropriate, further heteroatoms such as oxygen,sulfur or phosphorus atoms can also be comprised. The nitrogen atom is asuitable carrier of the positive charge in the cation of the ionicliquid, from which a proton or an alkyl radical can then be transferredin equilibrium to the anion so as to produce an electrically neutralmolecule.

If the nitrogen atom is the carrier of the positive charge in the cationof the ionic liquid, a cation can firstly be produced by quaternizationof the nitrogen atom of, for example, an amine or nitrogen heterocyclein the synthesis of the ionic liquids. The quaternization can beeffected by protonation of the nitrogen atom. Depending on theprotonation reagent used, salts having different anions are obtained. Incases in which it is not possible to form the desired anion directly inthe quaternization, this can be effected in a further step of thesynthesis. For example, starting from an ammonium halide, the halide canbe reacted with a Lewis acid to form a complex anion from the halide andLewis acid. As an alternative, it is possible to replace a halide ion bythe desired anion. This can be achieved by addition of a metal salt withprecipitation of the metal halide formed, by means of an ion exchangeror by displacement of the halide ion by a strong acid (with liberationof the hydrogen halide). Suitable methods are described, for example, inAngew. Chem. 2000, 112, pp. 3926-3945, and the references cited therein.

Preference is given to compounds which comprise at least one five- orsix-membered heterocycle, in particular a five-membered heterocycle,which has at least one nitrogen atom and, if appropriate, an oxygen orsulfur atom; particular preference is given to compounds which compriseat least one five- or six-membered heterocycle which has one, two orthree nitrogen atoms and a sulfur or oxygen atom, very particularlypreferably those having two nitrogen atoms. Preference is also given toaromatic heterocycles.

Particularly preferred compounds are ones which have a molecular weightof less than 1000 g/mol, very particularly preferably less than 500g/mol and in particular less than 250 g/mol.

Furthermore, preference is given to cations which are selected fromamong the compounds of the formulae (IVa) to (IVw),

and oligomers comprising these structures.

Further suitable cations are compounds of the general formulae (IVx) and(IVy)

and oligomers comprising this structure.

In the abovementioned formulae (IVa) to (IVy),

the radical R is hydrogen; and

the radicals R¹ to R⁹ are each, independently of one another, hydrogen,a sulfo group or a carbon-comprising organic, saturated or unsaturated,acyclic or cyclic, aliphatic, aromatic or araliphatic radical which hasfrom 1 to 20 carbon atoms and is unsubstituted or interrupted by from 1to 5 heteroatoms or functional groups or substituted, with the radicalsR¹ to R⁹ which are bound to a carbon atom (and not to a heteroatom) inthe abovementioned formulae (IV) also being able to be halogen or afunctional group; ortwo adjacent radicals from the group consisting of R¹ to R⁹ can togetheralso be a divalent, carbon-comprising organic, saturated or unsaturated,acyclic or cyclic, aliphatic, aromatic or araliphatic radical which hasfrom 1 to 30 carbon atoms and is unsubstituted or interrupted by from 1to 5 heteroatoms or functional groups or substituted.

In the definition of the radicals R¹ to R⁹, heteroatoms are in principleall heteroatoms which are formally able to replace a —CH₂—, —CH═, —C≡ or═C═ group. If the carbon-comprising radical comprises heteroatoms, thenpreference is given to oxygen, nitrogen, sulfur, phosphorus and silicon.Preferred groups are, in particular, —O—, —S—, —SO—, —SO₂—, —NR′—, —N═,—PR′—, —PR′₂ and —SiR′₂—, where the radicals R′ are the remaining partof the carbon-comprising radical. The radicals R¹ to R⁹ can in the casesin which they are bound to a carbon atom (and not to a heteroatom) inthe abovementioned formula (IV) also be bound directly via theheteroatom.

Possible functional groups are in principle all functional groups whichcan be bound to a carbon atom or a heteroatom. Examples of suitablefunctional groups are —OH (hydroxy), ═O (in particular as a carbonylgroup), —NH₂ (amino), ═NH (imino), —COOH (carboxy), —CONH₂(carboxamide), —SO₃H (sulfo) and —CN (cyano). Functional groups andheteroatoms can also be directly adjacent so that combinations of aplurality of adjacent atoms, for instance —O— (ether), —S— (thioether),—COO— (ester), —CONH— (secondary amide) or —CONR′— (tertiary amide) arealso comprised, for example di-(C₁-C₄-alkyl)amino,C₁-C₄-alkyloxycarbonyl or C₁-C₄-alkyloxy.

Halogens may be fluorine, chlorine, bromine and iodine.

The radicals R¹ to R⁹ are preferably, independently of one another,

-   -   hydrogen;    -   halogen;    -   a functional group;    -   C₁-C₁₈-alkyl which is optionally substituted by functional        groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms        and/or heterocycles and/or interrupted by one or more oxygen        and/or sulfur atoms and/or one or more substituted or        unsubstituted imino groups;    -   C₂-C₁₈-alkenyl which is optionally substituted by functional        groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms        and/or heterocycles and/or interrupted by one or more oxygen        and/or sulfur atoms and/or one or more substituted or        unsubstituted imino groups;    -   C₆-C₁₂-aryl which is optionally substituted by functional        groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms        and/or heterocycles;    -   C₅-C₁₂-cycloalkyl which is optionally substituted by functional        groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms        and/or heterocycles;    -   C₅-C₁₂-cycloalkenyl which is optionally substituted by        functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen,        heteroatoms and/or heterocycles; or    -   a five- or six-membered, oxygen-, nitrogen- and/or        sulfur-comprising heterocycle which is optionally substituted by        functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen,        heteroatoms and/or heterocycles; or        two adjacent radicals together form    -   an unsaturated, saturated or aromatic ring which is optionally        substituted by functional groups, aryl, alkyl, aryloxy,        alkyloxy, halogen, heteroatoms and/or heterocycles and        optionally interrupted by one or more oxygen and/or sulfur atoms        and/or one or more substituted or unsubstituted imino groups.

C₁-C₁₈-alkyl which is optionally substituted by functional groups, aryl,alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles ispreferably methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl,2-methyl-1-propyl (isobutyl), 2-methyl-2-propyl (tert-butyl), 1-pentyl,2-pentyl, 3-pentyl, 2-methyl-1-butyl, 3-methyl-1-butyl,2-methyl-2-butyl, 3-methyl-2-butyl, 2,2-dimethyl-1-propyl, 1-hexyl,2-hexyl, 3-hexyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl,4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl,4-methyl-2-pentyl, 2-methyl-3-pentyl, 3-methyl-3-pentyl,2,2-dimethyl-1-butyl, 2,3-dimethyl-1-butyl, 3,3-dimethyl-1-butyl,2-ethyl-1-butyl, 2,3-dimethyl-2-butyl, 3,3-dimethyl-2-butyl, heptyl,octyl, 2-etylhexyl, 2,4,4-tri-methylpentyl, 1,1,3,3-tetramethylbutyl,1-nonyl, 1-decyl, 1-undecyl, 1-dodecyl, 1-tridecyl, 1-tetradecyl,1-pentadecyl, 1-hexadecyl, 1-heptadecyl, 1-octadecyl, cyclopentylmethyl,2-cyclopentylethyl, 3-cyclopentylpropyl, cyclohexylmethyl,2-cyclohexylethyl, 3-cyclohexylpropyl, benzyl (phenylmethyl),diphenylmethyl (benzhydryl), triphenylmethyl, 1-phenylethyl,2-phenylethyl, 3-phenylpropyl, α,α-dimethylbenzyl, p-tolylmethyl,1-(p-butylphenyl)ethyl, p-chlorobenzyl, 2,4-dichlorobenzyl,p-methoxybenzyl, m-ethoxybenzyl, 2-cyanoethyl, 2-cyanopropyl,2-methoxycarbonylethyl, 2-ethoxycarbonylethyl, 2-butoxycarbonylpropyl,1,2-di(methoxycarbonyl)ethyl, methoxy, ethoxy, formyl,1,3-dioxolan-2-yl, 1,3-dioxan-2-yl, 2-methyl-1,3-dioxolan-2-yl,4-methyl-1,3-dioxolan-2-yl, 2-hydroxyethyl, 2-hydroxypropyl,3-hydroxypropyl, 4-hydroxybutyl, 6-hydroxyhexyl, 2-aminoethyl,2-aminopropyl, 3-aminopropyl, 4-aminobutyl, 6-aminohexyl,2-methylaminoethyl, 2-methylaminopropyl, 3-methylaminopropyl,4-methylaminobutyl, 6-methylaminohexyl, 2-dimethylaminoethyl,2-dimethylaminopropyl, 3-dimethylaminopropyl, 4-dimethylaminobutyl,6-dimethylaminohexyl, 2-hydroxy-2,2-dimethylethyl, 2-phenoxyethyl,2-phenoxypropyl, 3-phenoxypropyl, 4-phenoxybutyl, 6-phenoxyhexyl,2-methoxyethyl, 2-methoxypropyl, 3-methoxypropyl, 4-methoxybutyl,6-methoxyhexyl, 2-ethoxyethyl, 2-ethoxypropyl, 3-ethoxypropyl,4-ethoxybutyl, 6-ethoxyhexyl, acetyl, C_(n)F_(2(n-a)+(1-b))H_(2a+b)where n is from 1 to 30, 0≦a≦n and b=0 or 1 (for example CF₃, C₂F₅,CH₂CH₂—C_((n-2))F_(2(n-2)+1), C₆F₁₃, C₈F₁₇, C₁₀F₂₁, C₁₂F₂₅),chloromethyl, 2-chloroethyl trichloromethyl, 1,1-dimethyl-2-chloroethyl,methoxymethyl, 2-butoxyethyl, diethoxymethyl, diethoxyethyl,2-isopropoxyethyl, 2-butoxypropyl, 2-octyloxyethyl, 2-methoxyisopropyl,2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl,2-(n-butoxycarbonyl)ethyl, butylthiomethyl, 2-dodecylthioethyl,2-phenylthioethyl, 5-hydroxy-3-oxapentyl, 8-hydroxy-3,6-dioxaoctyl,11-hydroxy-3,6,9-trioxaundecyl, 7-hydroxy-4-oxaheptyl,11-hydroxy-4,8-dioxaundecyl, 15-hydroxy-4,8,12-trioxapentadecyl,9-hydroxy-5-oxanonyl, 14-hydroxy-5,10-dioxatetradecyl,5-methoxy-3-oxapentyl, 8-methoxy-3,6-dioxaoctyl,11-methoxy-3,6,9-trioxaundecyl, 7-methoxy-4-oxaheptyl,11-methoxy-4,8-dioxaundecyl, 15-methoxy-4,8,12-trioxapentadecyl,9-methoxy-5-oxanonyl, 14-methoxy-5,10-dioxatetradecyl,5-ethoxy-3-oxapentyl, 8-ethoxy-3,6-dioxaoctyl,11-ethoxy-3,6,9-trioxaundecyl, 7-ethoxy-4-oxaheptyl,11-ethoxy-4,8-dioxaundecyl, 15-ethoxy-4,8,12-trioxapentadecyl,9-ethoxy-5-oxanonyl or 14-ethoxy-5,10-oxatetradecyl.

C₂-C₁₈-Alkenyl which is optionally substituted by functional groups,aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocyclesand/or interrupted by one or more oxygen and/or sulfur atoms and/or oneor more substituted or unsubstituted imino groups is preferably vinyl,2-propenyl, 3-butenyl, cis-2-butenyl, trans-2-butenyl orC_(n)F_(2(n-a)−(1-b))H_(2a-b) where n≦30, 0≦a≦n and b=0 or 1.

C₆-C₁₂-Aryl which is optionally substituted by functional groups, aryl,alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles ispreferably phenyl, tolyl, xylyl, α-naphthyl, β-naphthyl, 4-diphenylyl,chlorophenyl, dichlorophenyl, trichlorophenyl, difluorophenyl,methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl,diethylphenyl, isopropylphenyl, tert-butylphenyl, dodecylphenyl,methoxyphenyl, dimethoxyphenyl, ethoxyphenyl, hexyloxyphenyl,methylnaphthyl, isopropylnaphthyl, chloronaphthyl, ethoxynaphthyl,2,6-dimethylphenyl, 2,4,6-trimethylphenyl, 2,6-dimethoxyphenyl,2,6-dichlorphenyl, 4-bromophenyl, 2-nitrophenyl, 4-nitrophenyl,2,4-dinitrophenyl, 2,6-dinitrophenyl, 4-dimethylaminophenyl,4-acetylphenyl, ethoxyethylphenyl, ethoxymethylphenyl, methylthiophenyl,isopropylthiophenyl or tert-butylthiophenyl or C₆F_((5-a))H_(a) where0≦a≦5.

C₅-C₁₂-Cycloalkyl which is optionally substituted by functional groups,aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocyclesis preferably cyclopentyl, cyclohexyl, cyclooctyl, cyclododecyl,methylcyclopentyl, dimethylcyclopentyl, methylcyclohexyl,dimethylcyclohexyl, diethylcyclohexyl, butylcyclohexyl,methoxycyclohexyl, dimethoxycyclohexyl, diethoxycyclohexyl,butylthiocyclohexyl, chlorocyclohexyl, dichlorocyclohexyl,dichlorocyclopentyl, C_(n)F_(2(n-a)−(1-b))H_(2a-b) where n≦30, 0≦a≦n andb=0 or 1 or a saturated or unsaturated bicyclic system such as norbornylor norbornenyl.

C₅-C₁₂-Cycloalkenyl which is optionally substituted by functionalgroups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/orheterocycles is preferably 3-cyclopentenyl, 2-cyclohexenyl,3-cyclohexenyl, 2,5-cyclohexadienyl or C_(n)F_(2(n-a)−3(1-b))H_(2a-3b)where n≦30, 0≦a≦n and b=0 or 1.

A five- or six-membered, oxygen-, nitrogen- and/or sulfur-comprisingheterocycle which is optionally substituted by functional groups, aryl,alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles ispreferably furyl, thiophenyl, pyrryl, pyridyl, indolyl, benzoxazolyl,dioxolyl, dioxyl, benzimidazolyl, benzthiazolyl, dimethylpyridyl,methylquinolyl, dimethylpyrryl, methoxyfuryl, dimethoxypyridyl ordifluoropyridyl.

If two adjacent radicals together form an unsaturated, saturated oraromatic ring which is optionally substituted by functional groups,aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocyclesand optionally interrupted by one or more oxygen and/or sulfur atomsand/or one or more substituted or unsubstituted imino groups, the tworadicals together are preferably 1,3-propylene, 1,4-butylene,1,5-pentylene, 2-oxa-1,3-propylene, 1-oxa-1,3-propylene,2-oxa-1,3-propylene, 1-oxa-1,3-propenylene, 3-oxa-1,5-pentylene,1-aza-1,3-propenylene, 1-C₁-C₄-alkyl-1-aza-1,3-propenylene,1,4-buta-1,3-dienylene, 1-aza-1,4-buta-1,3-dienylene or2-aza-1,4-buta-1,3-dienylene.

If the abovementioned radicals comprise oxygen and/or sulfur atomsand/or substituted or unsubstituted imino groups, the number of oxygenand/or sulfur atoms and/or imino groups is not subject to anyrestrictions. In general, there will be no more than 5 in the radical,preferably no more than 4 and very particularly preferably no more than3.

If the abovementioned radicals comprise heteroatoms, there is generallyat least one carbon atom, preferably at least two carbon atoms, betweenany two heteroatoms.

The radicals R¹ to R⁹ are particularly preferably, independently of oneanother,

-   -   hydrogen;    -   unbranched or branched C₁-C₁₈-alkyl which is unsubstituted or        substituted by one or more hydroxy, halogen, phenyl, cyano,        C₁-C₆-alkoxycarbonyl and/or sulfonic acid substituents and has a        total of from 1 to 20 carbon atoms, for example methyl, ethyl,        1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-1-propyl        (isobutyl), 2-methyl-2-propyl (tert-butyl), 1-pentyl, 2-pentyl,        3-pentyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2-methyl-2-butyl,        3-methyl-2-butyl, 2,2-dimethyl-1-propyl, 1-hexyl, 2-hexyl,        3-hexyl, 2-methyl-1-pentyl, 3-methyl-1-pentyl,        4-methyl-1-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl,        4-methyl-2-pentyl, 2-methyl-3-pentyl, 3-methyl-3-pentyl,        2,2-dimethyl-1-butyl, 2,3-dimethyl-1-butyl,        3,3-dimethyl-1-butyl, 2-ethyl-1-butyl, 2,3-dimethyl-2-butyl,        3,3-dimethyl-2-butyl, 1-heptyl, 1-octyl, 1-nonyl, 1-decyl,        1-undecyl, 1-dodecyl, 1-tetradecyl, 1-hexa-decyl, 1-octadecyl,        2-hydroxyethyl, benzyl, 3-phenylpropyl, 2-cyanoethyl,        2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl,        2-(n-butoxycarbonyl)ethyl, trifluoromethyl, difluoromethyl,        fluoromethyl, pentafluoroethyl, heptafluoropropyl,        heptafluoroisopropyl, nonafluorobutyl, nonafluoroisobutyl,        undecylfluoropentyl, undecylfluoroisopentyl, 6-hydroxyhexyl and        propylsulfonic acid;    -   glycols, butylene glycols and oligomers thereof having from 1 to        100 units and a hydrogen atom or a C₁-C₈-alkyl group as end        group, for example R^(A)O—(CHR^(B)—CH₂—O)_(n)—CHR^(B)—CH₂— or        R^(A)O—(CH₂CH₂CH₂CH₂O)_(n)—CH₂CH₂CH₂CH₂O— where R^(A) and R^(B)        are preferably hydrogen, methyl or ethyl and n is preferably        from 0 to 3, in particular 3-oxabutyl, 3-oxapentyl,        3,6-dioxaheptyl, 3,6-dioxaoctyl, 3,6,9-trioxadecyl,        3,6,9-trioxaundecyl, 3,6,9,12-tetraoxatridecyl and        3,6,9,12-tetraoxatetradecyl;    -   vinyl; and    -   N,N-di-C₁-C₆-alkylamino, for example N,N-dimethylamino and        N,N-diethylamino.

The radicals R¹ to R⁹ are very particularly preferably, independently ofone another, hydrogen or C₁-C₁₈-alkyl, for example methyl, ethyl,1-butyl, 1-pentyl, 1-hexyl, 1-heptyl, 1-octyl, phenyl, 2-hydroxyethyl,2-cyanoethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl,2-(n-butoxycarbonyl)ethyl, N,N-dimethylamino, N,N-diethylamino, chlorineor CH₃O—(CH₂CH₂O)_(n)—CH₂CH₂— and CH₃CH₂O—(CH₂CH₂O)_(n)—CH₂CH₂— where nis from 0 to 3.

Very particularly preferred pyridinium ions (IVa) are those in which

-   -   one of the radicals R¹ to R⁵ is methyl, ethyl or chlorine and        the remaining radicals R¹ to R⁵ are hydrogen;    -   R³ is dimethylamino and the remaining radicals R¹, R², R⁴ and R⁵        are hydrogen;    -   all radicals R¹ to R⁵ are hydrogen;    -   R² is carboxy or carboxamide and the remaining radicals R¹, R²,        R⁴ and R⁵ are hydrogen; or    -   R¹ and R² or R² and R³ are together 1,4-buta-1,3-dienylene and        the remaining radicals R¹, R², R⁴ and R⁵ are hydrogen;        and, in particular, those in which    -   R¹ to R⁵ are hydrogen; or    -   one of the radicals R¹ to R⁵ is methyl or ethyl and the        remaining radicals R¹ to R⁵ are hydrogen.

Very particularly preferred pyridinium ions (IVa) are pyridinium,2-methylpyridinium, 2-ethylpyridinium, 5-ethyl-2-methylpyridinium and2-methyl-3-ethylpyridinium.

Very particularly preferred pyridazinium ions (IVb) are those in which

-   -   R¹ to R⁴ are hydrogen; or    -   one of the radicals R¹ to R⁴ is methyl or ethyl and the        remaining radicals R¹ to R⁴ are hydrogen.

Very particularly preferred pyrimidinium ions (IVc) are those in which

-   -   R¹ is hydrogen, methyl or ethyl and R² to R⁴ are each,        independently of one another, hydrogen or methyl; or    -   R¹ is hydrogen, methyl or ethyl, R² and R⁴ are methyl and R³ is        hydrogen.

Very particularly preferred pyrazinium ions (IVd) are those in which

-   -   R¹ is hydrogen, methyl or ethyl and R² to R⁴ are each,        independently of one another, hydrogen or methyl;    -   R¹ is hydrogen, methyl or ethyl, R² and R⁴ are methyl and R³ is        hydrogen;    -   R¹ to R⁴ are methyl; or    -   R¹ to R⁴ are methyl or hydrogen.

Very particularly preferred imidazolium ions (IVe) are those in which

-   -   R¹ is hydrogen, methyl, ethyl, 1-propyl, 1-butyl, 1-pentyl,        1-hexyl, 1-octyl, 2-hydroxyethyl or 2-cyanoethyl and R² to R⁴        are each, independently of one another, hydrogen, methyl or        ethyl.

Very particularly preferred imidazolium ions (IVe) are1-methylimidazolium, 1-ethylimidazolium, 1-n-butylimidazolium,1-n-octylimidazolium, 1-n-dodecyl-imidazolium,1-n-tetradecylimidazolium, 1-n-hexadecylimidazolium,1,2-dimethyl-imidazolium, 1,4-dimethylimidazolium, 2-methylimidazolium,3-methylimidazolium, 3-etylimidazolium, 3-n-butylimidazolium,3-octylimidazolium, 4-methylimidazolium, 2-ethylimidazolium,1-vinylimidazolium, 1-n-octyl-4-methylimidazolium and1,4,5-trimethylimidazolium.

Very particularly preferred pyrazolium ions (IVf), (IVg) or (IVg′) arethose in which

-   -   R¹ is hydrogen, methyl or ethyl and R² to R⁴ are each,        independently of one another, hydrogen or methyl.

Very particularly preferred pyrazolium ions (IVh) are those in which

-   -   R¹ to R⁴ are each, independently of one another, hydrogen or        methyl.

As very particularly preferred pyrazolium ions, mention may be made ofpyrazolium and 1,4-dimethylpyrazolium.

In the process of the invention, very particularly preferred1-pyrazolinium ions (IVi) are those in which

-   -   R¹ to R⁶ are each, independently of one another, hydrogen or        methyl.

Very particularly preferred 2-pyrazolinium ions (IVj) or (IVj′) arethose in which

-   -   R¹ is hydrogen, methyl, ethyl or phenyl and R² to R⁶ are each,        independently of one another, hydrogen or methyl.

Very particularly preferred 3-pyrazolinium ions (IVk) or (IVk′) arethose in which

-   -   R¹ and R² are each, independently of one another, hydrogen,        methyl, ethyl or phenyl and R³ to R⁶ are each, independently of        one another, hydrogen or methyl.

Very particularly preferred imidazolinium ions (IVl) are those in which

-   -   R¹ and R² are each, independently of one another, hydrogen,        methyl, ethyl, 1-butyl or phenyl, R³ and R⁴ are each,        independently of one another, hydrogen, methyl or ethyl and R⁵        and R⁶ are each, independently of one another, hydrogen or        methyl.

Very particularly preferred imidazolinium ions (IVm) or (IVm′) are thosein which

-   -   R¹ and R² are each, independently of one another, hydrogen,        methyl or ethyl and R³ to R⁶ are each, independently of one        another, hydrogen or methyl.

Very particularly preferred imidazolinium ions (IVn) or (IVn′) are thosein which

-   -   R¹ to R³ are each, independently of one another, hydrogen,        methyl or ethyl and R⁴ to R⁶ are each, independently of one        another, hydrogen or methyl.

Very particularly preferred thiazolium ions (IVo) or (IVo′) andoxazolium ions (IVp) are those in which

-   -   R¹ is hydrogen, methyl, ethyl or phenyl and R² and R³ are each,        independently of one another, hydrogen or methyl.

Very particularly preferred 1,2,4-triazolium ions (IVq), (IVq′) or(IVq″) are those in which

-   -   R¹ and R² are each, independently of one another, hydrogen,        methyl, ethyl or phenyl and R³ is hydrogen, methyl or phenyl.

Very particularly preferred 1,2,3-triazolium ions (IVr), (IVr′) or(IVr″) are those in which

-   -   R¹ is hydrogen, methyl or ethyl and R² and R³ are each,        independently of one another, hydrogen or methyl, or R² and R³        are together 1,4-buta-1,3-dienylene.

Very particularly preferred pyrrolidinium ions (IVs) are those in which

-   -   R¹ is hydrogen, methyl, ethyl or phenyl and R² to R⁹ are each,        independently of one another, hydrogen or methyl.

Very particularly preferred imidazolidinium ions (IVt) are those inwhich

-   -   R¹ and R⁴ are each, independently of one another, hydrogen,        methyl, ethyl or phenyl and R² and R³ and also R⁵ to R⁸ are        each, independently of one another, hydrogen or methyl.

Very particularly preferred ammonium ions (IVu) are those in which

-   -   R¹ to R³ are each, independently of one another, C₁-C₁₈-alkyl;        or    -   R¹ and R² are together 1,5-pentylene or 3-oxa-1,5-pentylene and        R³ is C₁-C₁₈-alkyl, 2-hydroxyethyl or 2-cyanoethyl.

Examples of tertiary amines from which the quaternary ammonium ions ofthe general formula (IVu) are derived from quaternation by theabovementioned radical R are diethyl-n-butylamine,diethyl-tert-butylamine, diethyl-n-pentylamine, diethylhexylamine,diethyloctylamine, diethyl(2-ethylhexyl)amine, di-n-propylbutylamine,di-n-propyl-n-pentylamine, di-n-propylhexylamine, di-n-propyloctylamine,di-n-propyl(2-ethyl-hexyl)amine, diisopropylethylamine,diisopropyl-n-propylamine, diisopropylbutylamine,diisopropylpentylamine, diisopropylhexylamine, diisopropyloctylamine,diisopropyl(2-ethylhexyl)amine, di-n-butylethylamine,di-n-butyl-n-propylamine, di-n-butyl-n-pentylamine,di-n-butylhexylamine, di-n-butyloctylamine,di-n-butyl(2-ethylhexyl)amine, N-n-butylpyrrolidine,N-sec-butylpyrrolidine, N-tert-butylpyrrolidine, N-n-pentylpyrrolidine,N,N-dimethylcyclohexylamine, N,N-diethylcyclohexylamine,N,N-di-n-butylcyclohexylamine, N-n-propylpiperidine,N-isopropylpiperidine, N-n-butylpiperidine, N-sec-butylpiperidine,N-tert-butylpiperidine, N-n-pentylpiperidine, N-n-butylmorpholine,N-sec-butylmorpholine, N-tert-butylmorpholine, N-n-pentylmorpholine,N-benzyl-N-ethylaniline, N-benzyl-N-n-propylaniline,N-benzyl-N-isopropylaniline, N-benzyl-N-n-butylaniline,N,N-dimethyl-p-toluidene, N,N-diethyl-p-toluidene,N,N-di-n-butyl-p-toluidene, diethylbenzylamine, di-n-propylbenzylamine,di-n-butylbenzylamine, diethylphenylamine, di-n-propylphenylamine anddi-n-butylphenylamine.

Preferred tertiary amines (IVu) are diisopropylethylamine,diethyl-tert-butylamine, diisopropylbutylamine,di-n-butyl-n-pentylamine, N,N-di-n-butylcyclohexylamine and tertiaryamines derived from pentyl isomers.

Particularly preferred tertiary amines are di-n-butyl-n-pentylamine andtertiary amines derived from pentyl isomers. A further preferredtertiary amine which has three identical radicals is triallylamine.

Very particularly preferred guanidinium ions (IVv) are those in which

-   -   R¹ to R⁵ are methyl.

Very particularly preferred cholinium ions (IVw) are those in which

-   -   R¹ and R² are each, independently of one another, methyl, ethyl,        1-butyl or 1-octyl and R³ is hydrogen, methyl, ethyl, acetyl,        —SO₂OH or —PO(OH)₂;    -   R¹ is methyl, ethyl, 1-butyl or 1-octyl, R² is a —CH₂—CH₂—OR⁴        group and R³ and R⁴ are each, independently of one another,        hydrogen, methyl, ethyl, acetyl, —SO₂OH or —PO(OH)₂; or    -   R¹ is a —CH₂—CH₂—OR⁴ group, R² is a —CH₂—CH₂—OR⁵ group and R³ to        R⁵ are each, independently of one another, hydrogen, methyl,        ethyl, acetyl, —SO₂OH or —PO(OH)₂.

Particularly preferred cholinium ions (IVw) are those in which R³ isselected from among hydrogen, methyl, ethyl, acetyl,5-methoxy-3-oxapentyl, 8-methoxy-3,6-dioxaoctyl,11-methoxy-3,6,9-trioxaundecyl, 7-methoxy-4-oxaheptyl,11-methoxy-4,8-dioxaundecyl, 15-methoxy-4,8,12-trioxapentadecyl,9-methoxy-5-oxanonyl, 14-meth-oxy-5,10-oxatetradecyl,5-ethoxy-3-oxapentyl, 8-ethoxy-3,6-dioxaoctyl,11-ethoxy-3,6,9-trioxaundecyl, 7-ethoxy-4-oxaheptyl,11-ethoxy-4,8-dioxaundecyl, 15-ethoxy-4,8,12-trioxapentadecyl,9-ethoxy-5-oxanonyl or 14-ethoxy-5,10-oxatetradecyl.

Very particularly preferred phosphonium ions (IVx) are those in which

-   -   R¹ to R³ are each, independently of one another, C₁-C₁₈-alkyl,        in particular butyl, isobutyl, 1-hexyl or 1-octyl.

Among the abovementioned heterocyclic cations, the pyridinium ions,pyrazolinium ions, pyrazolium ions and imidazolinium ions and also theimidazolium ions are preferred. Preference is likewise given to ammoniumions. The metal cations [M¹]⁺, [M²]+, [M³]⁺, [M⁴]²⁺ and [M⁵]³⁺ mentionedin the formulae (IIIa) to (IIIj) are generally metal cations of groups1, 2, 6, 7, 8, 9, 10, 11, 12 and 13 of the Periodic Table. Suitablemetal cations are, for example, Li⁺, Na⁺, K⁺, Cs⁺, Mg²⁺, Ca²⁺, Ba²⁺,Cr³⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Zn²⁺ and Al³⁺.

As anions, it is in principle possible to use all anions.

The anion [Y]^(n−) of the ionic liquid is, for example, selected fromamong

the group of halides and halogen compounds of the formulae:

F⁻, Cl⁻, Br⁻, I⁻, BF₄ ⁻, PF₆ ⁻, AlCl₄ ⁻, Al₂Cl₇ ⁻, Al₃Cl₁₀ ⁻, AlBr₄ ⁻,FeC₄ ⁻, BCl₄ ⁻, SbF₆ ⁻, AsF₆, ⁻ZnCl₃ ⁻, SnCl₃ ⁻, CuCl₂ ⁻, CF₃SO₃ ⁻,(CF₃SO₃)₂N⁻, CF₃CO₂ ⁻, CCl₃CO₂ ⁻, CN⁻, SCN⁻, OCN⁻

the group of sulfates, sulfites and sulfonates of the general formulae:

SO₄ ²⁻, HSO₄ ⁻, SO₃ ²⁻, HSO₃ ⁻, R^(a)OSO₃ ⁻, R^(a)SO₃ ⁻

the group of phosphates of the general formulae

PO₄ ³⁻, HPO₄ ²⁻, H₂PO₄ ⁻, R^(a)PO₄ ²⁻, HR^(a)PO₄ ⁻, R^(a)R^(b)PO₄ ⁻

the group of phosphonates and phosphinates of the general formulae:

R^(a)HPO₃ ⁻, R^(a)R^(b)PO₂ ⁻, R^(a)R^(b)PO₃ ⁻

the group of phosphites of the general formulae:

PO₃ ³⁻, HPO₃ ²⁻, H₂PO₃ ⁻, R^(a)PO₃ ²⁻, R^(a)HPO₃ ⁻, R^(a)R^(b)PO₃ ⁻

the group of phosphonites and phosphinites of the general formulae:

R^(a)R^(b)PO₂ ⁻, R^(a)HPO₂ ⁻, R^(a)R^(b)PO⁻, R^(a)HPO⁻

the group of carboxylic acids of the general formula:

R^(a)COO⁻

the group of borates of the general formulae:

BO₃ ³⁻, HBO₃ ²⁻, H₂BO₃ ⁻, R^(a)R^(b)BO₃ ⁻, R^(a)HBO₃ ⁻, R^(a)BO₃ ²⁻,B(OR^(a))(OR^(b))(OR^(c))(OR^(d))⁻, B(HSO₄)⁻, B(R^(a)SO4)⁻

the group of boronates of the general formulae:

R^(a)BO₂ ²⁻, R^(a)R^(b)BO⁻

the group of carbonates and carbonic esters of the general formulae:

HCO₃ ⁻, CO₃ ²⁻, R^(a)CO₃ ⁻

the group of silicates and silicic esters of the general formulae:

SiO₄ ⁻, HSiO₄ ³⁻, H₂SiO₄ ²⁻, H₃SiO₄ ⁻, R^(a)SiO₄ ³⁻, R^(a)R^(b)SiO₄ ²⁻,R^(a)R^(b)R^(c)SiO₄ ⁻, HR^(a)SiO₄ ²⁻, H₂R^(a)SiO₄ ⁻, HR^(a)R^(b)SiO₄ ⁻

the group of alkyl silane and aryl silane salts of the general formulae:

R^(a)SiO₃ ³⁻, R^(a)R^(b)SiO₂ ²⁻, R^(a)R^(b)R^(c)SiO⁻,R^(a)R^(b)R^(c)SiO₃ ⁻, R^(a)R^(b)R^(c)SiO₂ ⁻, R^(a)R^(b)SiO₃ ²⁻

the group of carboximides, bis(sulfonyl)imides and sulfonylimides of thegeneral formulae:

the group of methides of the general formula:

the group of alkoxides and aryloxides of the general formula

-   -   R^(a)O⁻;        the group of halometalates of the general formula    -   [M_(q)Hal_(r)]^(s−),        -   where M is a metal and Hal is fluorine, chlorine, bromine or            iodine, q and r are positive integers and indicate the            stoichiometry of the complex and s is a positive integer and            indicates the charge on the complex;            the group of sulfides, hydrogen sulfides, polysulfides,            hydrogen polysulfides and thiolates of the general formulae:    -   S²⁻, HS⁻, [S_(v)]²⁻, [HS_(v)]⁻, [R^(a)S]⁻,    -   where v is a positive integer from 2 to 10;        the group of complex metal ions such as Fe(CN)₆ ³⁻, Fe(CN)₆ ⁴⁻,        MnO₄ ⁻, Fe(CO)₄ ⁻.

Here, R^(a), R^(b), R^(c) and R^(d) are each, independently of oneanother, hydrogen, C₁-C₃₀-alkyl, C₂-C₁₈-alkyl which is optionallyinterrupted by one or more nonadjacent oxygen and/or sulfur atoms and/orone or more substituted or unsubstituted imino groups, C₆-C₁₄-aryl,C₅-C₁₂-cycloalkyl or a five- or six-membered, oxygen-, nitrogen- and/orsulfur-comprising heterocycle, where two of them may together form anunsaturated, saturated or aromatic ring which is optionally interruptedby one or more oxygen and/or sulfur atoms and/or one or moreunsubstituted or substituted imino groups, where the radicals mentionedmay each be additionally substituted by functional groups, aryl, alkyl,aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles.

Here, C₁-C₁₈-alkyl which is optionally substituted by functional groups,aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocyclesis, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl,2,4,4-trimethylpentyl, decyl, dodecyl, tetradecyl, headecyl, octadecyl,1,1-dimethylpropyl, 1,1-dimethylbutyl, 1,1,3,3-tetramethylbutyl, benzyl,1-phenylethyl, α,α-dimethylbenzyl, benzhydryl, p-tolylmethyl,1-(p-butylphenyl)ethyl, p-chlorobenzyl, 2,4-dichlorobenzyl,p-methoxybenzyl, m-ethoxybenzyl, 2-cyanoethyl, 2-cyanopropyl,2-methoxycarbonylthyl, 2-ethoxycarbonylethyl, 2-butoxycarbonylpropyl,1,2-di-(methoxycarbonyl)ethyl, 2-methoxyethyl, 2-ethoxyethyl,2-butoxyethyl, diethoxymethyl, diethoxyethyl, 1,3-dioxolan-2-yl,1,3-dioxan-2-yl, 2-methyl-1,3-dioxolan-2-yl, 4-methyl-1,3-dioxolan-2-yl,2-isopropoxyethyl, 2-butoxypropyl, 2-octyloxyethyl, chloromethyl,trichloromethyl, trifluoromethyl, 1,1-dimethyl-2-chloroethyl,2-methoxyisopropyl, 2-eth-oxyethyl, butylthiomethyl, 2-dodecylthioethyl,2-phenlythioethyl, 2,2,2-trifluoroethyl, 2-hydroxyethyl,2-hydroxypropyl, 3-hydroxypropyl, 4-hydroxybutyl, 6-hydroxyhexyl,2-aminoethyl, 2-aminopropyl, 4-aminobutyl, 6-aminohexyl,2-methylaminoethyl, 2-methylaminopropyl, 3-methylaminopropyl,4-methylaminobutyl, 6-methylaminohexyl, 2-dimethylaminoethyl,2-dimethylaminopropyl, 3-dimethylaminopropyl, 4-dimethyl-aminobutyl,6-dimethylaminohexyl, 2-hydroxy-2,2-dimethylethyl, 2-phenoxyethyl,2-phenoxypropyl, 3-phenoxypropyl, 4-phenoxybutyl, 6-phenoxyhexyl,2-methoxyethyl, 2-methoxypropyl, 3-methoxypropyl, 4-methoxybutyl,6-methoxyhexyl, 2-ethoxyethyl, 2-ethoxypropyl, 3-ethoxypropyl,4-ethoxybutyl or 6-ethoxyhexyl.

C₂-C₁₈-Alkyl which is optionally substituted by one or more nonadjacentoxygen and/or sulfur atoms and/or one or more substituted orunsubstituted imino groups is, for example, 5-hydroxy-3-oxapentyl,8-hydroxy-3,6-dioxaoctyl, 11-hydroxy-3,6,9-tri-oxaundecyl,7-hydroxy-4-oxaheptyl, 11-hydroxy-4,8-dioxaundecyl,15-hydroxy-4,8,12-trioxapentadecyl, 9-hydroxy-5-oxanonyl,14-hydroxy-5,10-oxatetradecyl, 5-methoxy-3-oxapentyl,8-methoxy-3,6-dioxaoctyl, 11-methoxy-3,6,9-trioxaundecyl,7-methoxy-4-oxaheptyl, 11-methoxy-4,8-dioxaundecyl,15-methoxy-4,8,12-trioxapentadecyl, 9-methoxy-5-oxanonyl,14-methoxy-5,10-oxatetradecyl, 5-ethoxy-3-oxapentyl,8-ethoxy-3,6-dioxaoctyl, 11-ethoxy-3,6,9-trioxaundecyl,7-ethoxy-4-oxaheptyl, 11-ethoxy-4,8-dioxaundecyl,15-ethoxy-4,8,12-trioxapentadecyl, 9-ethoxy-5-oxanonyl or14-ethoxy-5,10-oxatetradecyl.

If two radicals form a ring, these radicals can together form, forexample, 1,3-propylene, 1,4-butylene, 2-oxa-1,3-propylene,1-oxa-1,3-propylene, 2-oxa-1,3-propenylene, 1-aza-1,3-propenylene,1-C₁-C₄-alkyl-1-aza-1,3-propenylene, 1,4-buta-1,3-dienylene,1-aza-1,4-buta-1,3-dienylene or 2-aza-1,4-buta-1,3-dienylene as fused-onbuilding block.

The number of nonadjacent oxygen and/or sulfur atoms and/or imino groupsis in principle not subject to any restrictions or is automaticallyrestricted by the size of the radical or the cyclic building block. Ingeneral, it will be no more than 5 in the respective radical, preferablyno more than 4 and very particularly preferably no more than 3.Furthermore, there is generally at least one carbon atom, preferably atleast two carbon atoms, between any two heteroatoms.

Substituted and unsubstituted imino groups can be, for example, imino,methylimino, isopropylimino, n-butylimino or tert-butylimino.

For the purposes of the present invention, the term “functional groups”refers, for example, to the following: carboxy, carboxamide, hydroxy,di-(C₁-C₄-alkyl)amino, C₁-C₄-alkyloxycarbonyl, cyano or C₁-C₄-alkoxy.Here, C₁C₄-alkyl is methyl, ethyl, propyl, isopropyl, n-butyl, sec-butylor tert-butyl.

C₆-C₁₄-Aryl which is optionally substituted by functional groups, aryl,alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles is,for example, phenyl, tolyl, xylyl, α-naphthyl, β-naphthyl, 4-diphenylyl,chlorophenyl, dichlorophenyl, trichlorophenyl, difluorophenyl,methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl,diethylphenyl, isopropylphenyl, tert-butylphenyl, dodecylphenyl,methoxyphenyl, dimethoxyphenyl, ethoxyphenyl, hexyloxyphenyl,methylnaphthyl, isopropyinaphthyl, chloronaphthyl, ethoxynaphthyl,2,6-dimethylphenyl, 2,4,6-trimethylphenyl, 2,6-dimethoxyphenyl,2,6-dichlorophenyl, 4-bromophenyl, 2- or 4-nitrophenyl, 2,4- or2,6-dinitrophenyl, 4-dimethylaminophenyl, 4-acetylphenyl,methoxyethylphenyl or ethoxymethylphenyl.

C₅-C₁₂-Cycloalkyl which is optionally substituted by functional groups,aryl, alkyl, aryloxy, halogen, heteroatoms and/or heterocycles is, forexample, cyclopentyl, cyclohexyl, cyclooctyl, cyclododecyl,methylcyclopentyl, dimethylcyclopentyl, methylcyclohexyl,dimethylcyclohexyl, diethylcyclohexyl, butylcyclohexyl,methoxycyclohexyl, dimethoxycyclohexyl, diethoxycyclohexyl,butylthiocyclohexyl, chlorocyclohexyl, dichlorocyclohexyl,dichlorocyclopentyl or a saturated or unsaturated bicyclic system suchas norbornyl or norbornenyl.

A five- or six-membered, oxygen-, nitrogen- and/or sulfur-comprisingheterocycle is, for example, furyl, thiophenyl, pyryl, pyridyl, indolyl,benzoxazolyl, dioxolyl, dioxyl, benzimidazolyl, benzthiazolyl,dimethylpyridyl, methylquinolyl, dimethylpyryl, methoxyfuryl,dimethoxypyridyl, difluoropyridyl, methylthiophenyl, isopropylthiophenylor tert-butylthiophenyl.

Preferred anions are selected from the group of halides andhalogen-comprising compounds, the group of carboxylic acids, the groupof sulfates, sulfites and sulfonates and the group of phosphates.

Preferred anions are chloride, bromide, iodide, SCN⁻, OCN⁻, CN⁻,acetate, C₁-C₄-alkylsulfates, R^(a)—COO⁻, R^(a)SO₃ ⁻, R^(a)R^(b)PO₄ ⁻,methanesulfonates, tosylate, C₁-C₄-dialkylphosphates, hydrogen sulfateor tetrachloroaluminate.

Particularly preferred anions are Cl⁻, CH₃COO⁻ or CH₃SO₃ ⁻.

Both cations and anions are present in the ionic liquid. Within theionic liquid, a proton or an alkyl radical is transferred from thecation to the anion. This forms two uncharged molecules. There is thusan equilibrium in which anions, cations and the two uncharged moleculesformed therefrom are present.

The solution preferably has a temperature of not more than 180° C. Thesolution of the present invention more preferably has a temperature ofnot more than 160° C., even more preferably not more than 120° C. andparticularly preferably not more than 100° C.

The present invention further provides a process for preparing asolution according to the invention, which comprises the steps

-   -   a) addition of cellulose to a solution comprising an ionic        liquid comprising anions and cations as solvent, wherein the        cations comprise at least one nitrogen atom which is present in        protonated form as ammonium cation    -   b) mixing of the solution until the cellulose is completely        dissolved.

Mixing is preferably carried out by means of stirring, shaking and/orwith the aid of microwaves.

The dissolution preferably occurs within 3 days, more preferably withinone day and particularly preferably within 12 hours.

The present invention further provides for the use of a solutionaccording to the present invention for the physical or chemicaltreatment of cellulose.

The chemical treatment can comprise oxidation, reduction, pyrolysis,hydrolysis, isomeration, sterification, alkoxylation orcopolymerization.

The present invention is illustrated by means of the following examples.

EXAMPLES Example 1

0.78 g of newsprint are cut into pieces having a size of about 1 cm²,admixed with 10.0 g of 1-methylimidazole hydrochloride(1-methylimidazolium chloride) and stirred at 120° C. After 23 hours,the paper has dissolved completely.

Example 2

7.8 g of filter paper (blue band filter) are cut into pieces having asize of about 1 cm², admixed with 100 g of 1-methylimidazolhydrochloride and stirred at 95° C. After 72 hours, the paper hasdissolved completely.

1. A solution comprising cellulose and an ionic liquid comprising one ormore anions and one or more cations as solvent, wherein the one or morecations comprise at least one atom selected from the group consisting ofnitrogen, oxygen, sulfur and phosphorus which is present in protonatedform, and wherein the ionic liquid comprises at least one cationselected from the group consisting of formulae (IVe) to (IVt):

and oligomers comprising one or more of formulae (IVe) to (IVt), whereinR is hydrogen; and R¹ to R⁹ are each, independently of one another,hydrogen, a sulfo group or a carbon-comprising organic, saturated orunsaturated, acyclic or cyclic, aliphatic, aromatic or araliphaticradical which has from 1 to 20 carbon atoms and is unsubstituted orinterrupted by from 1 to 5 heteroatoms or functional groups orsubstituted, with the radicals R¹ to R⁹ which are bound to a carbon atom(and not to a heteroatom) in the formulae (IV) also being able to behalogen or a functional group; or two adjacent radicals from the groupconsisting of R¹ to R⁹ can together also be a divalent,carbon-comprising organic, saturated or unsaturated, acyclic or cyclic,aliphatic, aromatic or araliphatic radical which has from 1 to 30 carbonatoms and is unsubstituted or interrupted by from 1 to 5 heteroatoms orfunctional groups or substituted.
 2. The solution according to claim 1,wherein the one or more cations comprise at least one nitrogen atomwhich is present in protonated form as an ammonium cation.
 3. Thesolution according to claim 1, wherein said solution comprises more than1% by weight of cellulose, based on the total weight of the solution. 4.The solution according to claim 1, wherein said one or more anions andsaid one or more cations form: a salt of formula (I)[A]_(n) ⁺[Y]^(n−)  (I), where n is 1, 2, 3 or 4, [A]⁺ is a quaternaryammonium cation, an oxonium cation, a sulfonium cation or a phosphoniumcation and [Y]^(n−) is a monovalent, divalent, trivalent or tetravalentanion; or mixed salts of formulae (II)[A¹]⁺[A²]⁺[Y]^(n−)  (IIa), where n=2;[A¹]⁺[A²]⁺[A³]⁺[Y]^(n−)  (IIb), where n=3; or[A¹]⁺[A²]⁺[A³]⁺[A⁴]⁺[Y]^(n−)  (IIc), where n=4, and where [A¹]⁺, [A²]⁺,[A³]⁺ and [A⁴]⁺ are selected independently from among the groupsmentioned for [A]⁺, and [Y]^(n−) is as defined in formula (I); or mixedsalts of formulae (III)[A¹]⁺[A²]⁺[A³]⁺[M¹]⁺[Y]^(n−)  (IIIa), where n=4;[A¹]⁺[A²]⁺[M¹]⁺[M²]⁺[Y]^(n−)  (IIIb), where n=4;[A¹]⁺[M¹]⁺[M²]⁺[M³]⁺[Y]^(n−)  (IIIc), where n=4;[A¹]⁺[A²]⁺[M¹]⁺[Y]^(n−)  (IIId), where n=3;[A¹]⁺[M¹]⁺[M²]⁺[Y]^(n−)  (IIIe), where n=3;[A¹]⁺[M¹]⁺[Y]^(n−)  (IIIf), where n=2;[A¹]⁺[A²]⁺[M⁴]²⁺[Y]^(n−)  (IIIg), where n=4;[A¹]⁺[M¹]⁺[M⁴]²⁺[Y]^(n−)  (IIIh), where n=4;[A¹]⁺[M⁵]³⁺[Y]^(n−)  (IIIi), where n=4; or[A¹]⁺[M⁴]²⁺[Y]^(n−)  (IIIj), where n=3, and where [A¹]⁺, [A²]⁺ and [A³]⁺are selected independently from among the groups mentioned for [A]⁺,[Y]^(n−) is as defined in formula (I) and [M¹]⁺, [M²]⁺, [M³]⁺ aremonovalent metal cations, [M⁴]²⁺ is a divalent metal cation and [M⁵]³⁺is a trivalent metal cation.
 5. The solution according to claim 1,wherein the ionic liquid comprises at least one anion selected from thegroup consisting of: the group of halides and halogen compounds of theformulae: F⁻, Cl⁻, Br⁻, I⁻, BF₄ ⁻, PF₆ ⁻, AlCl₄ ⁻, Al₂Cl₇ ⁻, Al³Cl₁₀ ⁻,AlBr₄, FeCl₄ ⁻, BCl₄ ⁻, SbF₆ ⁻, AsF₆ ⁻, ⁻ZnCl₃ ⁻, SnCl₃ ⁻, CuCl₂ ⁻,CF₃SO₃ ⁻, (CF₃SO₃)₂N⁻, CF₃CO₂ ⁻, CCl₃CO₂ ⁻, CN⁻, SCN⁻, OCN⁻; the groupof sulfates, sulfites and sulfonates of the formulae: SO₄ ²⁻, HSO₄ ⁻,SO₃ ²−, HSO₃ ⁻, R^(a)OSO₃ ⁻, R^(a)SO₃ ⁻; the group of phosphates of theformulae: PO₄ ³⁻, HPO₄ ²⁻, H₂PO₄ ⁻, R^(a)PO₄ ²⁻, HR^(a)PO₄ ⁻,R^(a)R^(b)PO₄ ⁻; the group of phosphonates and phosphinates of theformulae: R^(a)HPO₃ ⁻, R^(a)R^(b)PO₂ ⁻, R^(a)R^(b)PO₃ ⁻; the group ofphosphites of the formulae: PO₃ ³⁻, HPO₃ ²⁻, H₂PO₃ ⁻, R^(a)PO₃ ²⁻,R^(a)HPO₃ ⁻, R^(a)R^(b) PO₃ ⁻; the group of phosphonites andphosphinites of the formulae: R^(a)R^(b)PO₂ ⁻, R^(a)HPO₂ ⁻,R^(a)R^(b)PO⁻, R^(a)HPO⁻; the group of carboxylic acids of the formula:R^(a)COO⁻; the group of borates of the formulae: BO₃ ³⁻, HBO₃ ²⁻, H₂BO₃⁻, R^(a)R^(b)BO₃ ⁻, R^(a)HBO₃ ⁻, R^(a)BO₃ ²⁻,B(OR^(a))(OR^(b))(OR^(c))(OR^(d))⁻, B(HSO₄, ⁻, B(R^(a)SO4)⁻; the groupof boronates of the formulae: R^(a)BO₂ ²⁻, R^(a)R^(b)BO⁻; the group ofcarbonates and carbonic esters of the formulae: HCO₃ ⁻, CO₃ ²⁻, R^(a)CO₃⁻; the group of silicates and silicic esters of the formulae: SiO₄ ⁴⁻,HSiO₄ ³⁻, H₂SiO₄ ²⁻, H₃SiO₄ ⁻, R^(a)SiO₄ ³⁻, R^(a)R^(b)SiO₄ ²⁻,R^(a)R^(b)R^(c)SiO₄ ⁻, HR^(a)SiO₄ ²⁻, H₂R^(a)SiO₄ ⁻, HR^(a)R^(b)SiO₄ ⁻;the group of alkyl silane and aryl silane salts of the formulae:R^(a)SiO₃ ³⁻, R^(a)R^(b)SiO₂ ²⁻, R^(a)R^(b)R^(c)SiO⁻,R^(a)R^(b)R^(c)SiO₃ ⁻, R^(a)R^(b)R^(c)SiO₂ ⁻, R^(a)R^(b)SiO₃ ²⁻; thegroup of carboximides, bis(sulfonyl)imides and sulfonylimides of theformulae:

the group of methides of the formula:

the group of alkoxides and aryloxides of the formula; R^(a)O⁻; the groupof halometalates of the general formula: [M_(q)Hal_(r)]^(s−), where M isa metal and Hal is fluorine, chlorine, bromine or iodine, q and r arepositive integers and indicate the stoichiometry of the complex and s isa positive integer and indicates the charge on the complex; the group ofsulfides, hydrogen sulfides, polysulfides, hydrogen polysulfides andthiolates of the formulae: S²⁻, HS⁻, [S_(v)]²⁻, [HS_(v)]⁻, [R^(a)S]⁻,where v is a positive integer from 2 to 10; and the group of complexmetal ions such as Fe(CN)₆ ³⁻, Fe(CN)₆ ⁴⁻, MnO₄ ⁻, Fe(CO)₄ ⁻, whereR^(a), R^(b)R^(c) and R^(d) are each, independently of one another,hydrogen, C₁-C₁₈-alkyl, C₂-C₁₈-alkyl which is optionally interrupted byone or more nonadjacent oxygen and/or sulfur atoms and/or one or moresubstituted or unsubstituted imino groups, C₆-C₁₄-aryl,C₅-C₁₂-cycloalkyl or a five- or six-membered, oxygen-, nitrogen- and/orsulfur-comprising heterocycle, where two of them may together form anunsaturated, saturated or aromatic ring which is optionally interruptedby one or more oxygen and/or sulfur atoms and/or one or moreunsubstituted or substituted imino groups, where the radicals mentionedmay each be additionally substituted by functional groups, aryl, alkyl,aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles.
 6. Thesolution according to claim 1 which has a temperature of not more than180° C.
 7. A process for preparing a solution according to claim 1,which comprises: a) adding cellulose to a solution comprising the ionicliquid according to claim 1, and b) mixing of the solution until thecellulose is completely dissolved.
 8. A method for the physical orchemical treatment of cellulose comprising treating cellulose with theionic liquid according to claim 1.